Task #7

You can see the light and dark spots, which works by the process of diffraction grating. A diffraction grating is an optical grating with a periodic structure that diffracts light into several beams traveling in different directions; hence why you see light and dark beams of light. 

We built a beam expander, then placed a pin in front of the laser and aligned it until we found Poisson's spot. When light shines on a small, solid object, such as a pin in this example, it would be predicted that the shadow should be completely dark. However, Poisson's spot contradicts this expectation. The phenomenon occurs because of the wave nature of light. There is a tiny light spot in the middle of the dark shadow, which exists because of diffraction.